Vulcanization of rubber



UNITED STATES A'I'Elfl'l' OFFICE VULCANIZATION OF RUBBER Paul C. Jonesand Roger A. Mathes, Akron, Ohio, assignors to The B. F. GoodrichCompany, New York, N. Y., a corporation of New York No Drawing.Application February 8, 193 Serial No. 255,357

14 Claims. (C1. 25il--'738) This invention relates to the vulcanizationof other than hydrocarbon constituents are not inrubber, and to rubbercompositions vulcanized in cluded Within the scope of this inventionsince the presence of the accelerators herein described. they are nottrue polyamines.

. It has long been known that rubber may be 7 The products of thisinvention are prepared by vulcanized in reduced times in the presence ofthe ordinary methods well known to the art. materials commonly calledaccelerators. It is Thus, when alcoholic solutions of 2-mercaptoobjectof this invention to provide a new and eX- thiazcline and ethylenediamine are mixed in ceedingly effective class of accelerators. 1:1 or2:1 ratio, an exothermic reaction occurs, It has previously beenobserved that the class and the product is isolated as a viscous syrup.of compounds known as Z-mercaptothiazolines, The salts of the higheramines such as triethylene of which the simplest member has thestructural tetramine may be formed by reacting Z-mercapformulatothiazoline and triethylene tetramine in equi- 4 3 molar ratios, or inhigher ratios such as 2:1, 3:1,

mCWN 2 or 4:1.

L Rubber compositions accelerated with the polyamino salts ofZ-mercaptothiazolines exhibit a 5 1 very fiat rate of cure, an advantagenot possessed that 2-mercaptothiazolines are good accelerators whenemployed in the presence of carboxylic by either polyamines orZ-mercaptothiazolines when employed as accelerators. The outstandgo ingperformance of the accelerators of this invention in this respect isillustrated by tests in which a rubber composition containing rubber 100parts by weight, zinc oxide 5 parts, sulfur 3 parts, stearic acid 1part, and 1 part of the 1:1 salt of Z-mercaptothiazoline and triethylenetetramine was prepared. When the composition was cured in a heated moldfor varying times at 287 F., compositions having the following tensilestrengths in lbs. per square inch and elonga- 39 tions in percent Wereobtained:

are poor accelerators of vulcanization.

We have disclosed in our copending application Serial No. 255,358, filedFebruary 8, 1939,

acids and their metallic salts.

Although the quaternary ammonium salts of 2-mercaptothiazolines areknown to exist, we have found that, in general, the amine salts of2-mercaptothiazolines cannot be prepared. The tendency forZ-mercaptothiazolines to combine with mono-amine bases as strong asdiethylamine and cyclohexylamine is so slight that it has not beenpossible to isolate the diethylammonium or cyclohexyl-ammonium salts ofZ-mercaptothiazoline.

Time of cure in minutes T E We have now discovered that the polyaminesalts of 2-mercaptothiazo1ine may be prepared and isolated, and thatthese materials are excellent accelerators of vulcanization, even in theM absence of any carboxylic acid It can be seen that tn1s COmpOS1'bl01'lexhi ited A Wide variety of polyamine salts of z a remarkable freedomfrom over-cure, even in 90 tothiazoline or related compounds containing40 minutes at 287 F. Similar results are obtained substituents otherthan hydrogen on the arbgn with other accelerators within the scope ofthis atoms y be ployed. It is preferred to eminventlon- 1 ploy aliphaticpglyamines containing two It is not essential to tuc successful pract cemore primary amino groups such as ethylene of my lhvehii-lon h t t e tsbe prepared prior d mi butylene i 1,4- 1 to the incorporation in therubber composition. hexane, 1,3,5-triamino cyclohexane, tri-amino- Thus,if 2me1CaptOth1aZ011ne a d et ylene d1- ethyl amine, di(beta-aminoethyl)amine, triamine are incorporated in a ubber composit on, ethylenetetramine, etc. Aromatic polyamines the t i l be or ed in sltu durlngvulcanizacontaining at least two primary amino groups Dion a d the rateof cure of the composition W111 such as phenylene diamine (ortho, meta,or approximate that which would have been obpara), naphthylene diamine(1,2-, 1,4-, 1,5-, 1,6-, tained had the salt been preparedbefore incor-1,7-,1,8-,2,3-,or2,6-,), benzidine,to1idine (ortho, poration in therubber. It is believed, though meta, or para), etc., may also be used.we do not wish to be bound by our theory, that Amides and amidines suchas urea and guanithe p y s ay be re as act vators for dine containingNHZ groups separated b grQupS the 2-rnercapto-thiazolines. It has beenobserved that other basic nitrogenous accelerators which do not requireacidic activation such as diphenyl guanidine react in the same manner asthe polyamine. It has been noted, however, that compositions having theextraordinary resistance to overcure exhibited by the vulcanizates ofthis invention are not produced by any of the other salts ofZ-mercaptothiazolines with bases within the class mentioned.

Although the use of the accelerators of this invention has beendescribed in detail in con- 7 nection with specific rubber compositions,it will be evident that this invention is applicable to rubbercompositions of the most varied nature, and that all manner of rubbergoods including pneumatic and solid rubber tires, tubes, hose, belting,packing, boots and shoes, surgical rubber goods, seamless dipped rubberarticles, etc. may be vulcanized in the presence of the acceleratorsherein described. The accelerator may be incorporated in the rubber bymastication, milling or any similar process, or in the case oflatex,rubber cement, or any other natural or artificial dispersion or solutionof rubber by simply dissolving or suspending the accelerator therein.

The vulcanization may be performed in other manners than thatparticularly set forth in the specific examples; specifically, rubbercompositions may be heated in the presence of sulfur or selenium in hotair, steam, hot Water, etc.

It is to be understood that the term a rubber is employed in theappended claims in a generic sense to designate those rubbery materialswhich are vulcanizable with sulfur, including caoutchouc, balata, guttapercha, latex, rubber isomers, or synthetic rubber whether or notadmixed with pigments, fillers, softeners, antioxidants, otheraccelerators, etc., but not including materials incapable ofvulcanization by reaction with sulfur.

While we have herein disclosed specific embodiments of our invention, wedo not intend to limit ourselves solely thereto, for it will be obviousto those skilled in the art that many modifications such as using othermaterials having equivalent properties and varying the proportions ofmaterials used are within the spirit and scope of the invention asdefined in the appended claims.

We claim:

1. The process which comprises vulcanizing a rubber in the presence of asalt in which a 2- mercaptothiazoline is combined with a polyaminecontaining at least two primary amino groups.

2. The process which comprises vulcanizing a rubber in the presence of asalt in which a 2- mercaptothiazoline is combined with an aliphaticpolyamine containing at least two primary amino groups.

3. The process which comprises vulcanizing a rubber in the presence ofalkylene diamine salt of Z-mercaptothiazoline.

4. The process which comprises vulcanizing a rubber in the presence ofan ethylene diamine salt of 2-mercaptothiazoline.

5. The process which comprises vulcanizing a rubber in the presence of atrialkylene tetramine salt of 2-mercaptothiazoline.

6. The process which comprises vulcanizing a rubber in the presence of atriethylene'tetramine salt of Z-mercaptothiazoline.

7. A rubber which has been vulcanized in the presence of a salt in whicha 2-mercaptothiazo-' line is combined with a polyamine containing atleast two primary amino groups.

8. A rubber which has been vulcanized in the presence of a salt in whicha Z-mercaptothiazoline is combined with an aliphatic polyaminecontaining at least two primary amino groups.

9. A rubber which has been Vulcanized in the presence of an alkylenediamine salt of 2-mercaptothiazoline.

10. A rubber which has been vulcanized in the presence of an ethylenediamine salt of 2-mercaptothiazoline.

11. A rubber which has been vulcanized in the presence of a trialkylenetetramine salt of 2- mercaptothiazoline.

12. A rubber which has been vulcanized in the presence of a triethylenetetramine salt of 2- mercaptothiazoline.

13. The process which comprises vulcanizing a rubber in the presence ofa polyethylene polyamine salt of 2-mercaptothiazoline.

14. A rubber which has been vulcanized in the presence of a polyethylenepolyamine salt of 2- mercapthiazoline.

PAUL C. JONES. ROGER A. MATI-IES.

